Means for operating a valve or the like in accordance



March 24, 1964 Original Filed March 13, L959 2 Sheets-Sheet l g iu y 5 na m 09: E W? m 7 0 E6 T nfi\\k 4v P J T m m a A M4 M a e .r W W? RAW v 64 fl. m Q Q 1 i 0 3 M WNW i ir/ mm x A Q NV r 5w k March 24, 1964 R. P.SWEGER ETAL Re. 25,540

MEANS FOR OPERATING A VALVE OR THE LIKE IN ACCORDANCE WITH A CONTROLLEDCONDITION Original Filed March 13, 1959 2 Sheets-Sheet 2 0 5 9 r n Y a Im w m Wm M 1 flws u r w w H r MGRA f A mu /W 433G hzuuwab 4(20. .5555 ae 6! Em: \:3m& in; bfiu L M s FM V a ,7 M w a a RAM 3 a i 2 RA 7 w o 5 j4 M 4 6 .imxzzu 4535 E6255 4.22% EMES EE \EGm r .55: 23mm ii 5 4 m3 4 aa I n 7 r 4mg m E 7/ F/ United States Patent MEANS FOR OPERATING A VALVEOR THE LIKE IN ACCORDANCE WITH A CONTROLLED CONDITION Russell P. Swegerand Alfred A. Horton, Rockford, and

William G. Young, Loves Park, Ill., assignors to Barber- Colman Company,Rockford, Ill., a corporation of Illinois Original No. 3,050,257, datedAug. 21, 1962, Ser. No. 799,274, Mar. 13, 1959. Application for reissueDec. 11, 1962, Ser. No. 244,547

7 Claims. (Cl. 236-74) Matter enclosed in heavy brackets [1 appears inthe original patent but forms no part of this reissue Specification;matter printed in italics indicates the additions made by reissue.

The present invention relates to condition control systems and moreparticularly to a combined control and power unit for use in connectionwith a radiator valve, damper element or the like.

It is an object of the present invention to provide novel conditioncontrol means which is distinguished by extreme compactness combinedwith a high degree of reliability. It is a related object to provide anovel control means intended for use with a radiator valve or the likewhich is characterized by use of a low power level and low current drainbut which is nevertheless capable of developing large forces for theoperation and positioning of a radiator valve and for overcoming anytendency for the valve or valve packing to stick, particularly after anextended period of non-use. It is a related object to provide a unitaryvalve operator incorporating an amplifier and driving means, whichrequires only connection to a remote condition sensitive element and AC.supply line, which may be mounted on the radiator, and which occupiesonly slightly more space than the motor and gear driving trainconventionally employed to operate radiator valves.

It is a related object to provide a unitary valve operator employing anovel arrangement of parts, with the amplifier and motor assembly beingwrapped around and supported by the hydraulic valve actuator.

It is another object to provide a novel amplifying arrangement includinga transistor amplifier to obtain additional amplification and anhydraulic amplifier to develop large forces with a low power motor andwithout the necessity for using step-down gearing. It is a more specificobject to provide a valve operator which employs a constantly runningpump driven by a low torque A.-C. motor with electromagnetic means forvarying the pressure applied to an associated hydraulic actuator, butwhich is capable of developing large total force with low controlcurrents, permitting use of low power inexpensive transistor circuits.It is another specific object to provide a constantly running hydrauliccontrol arrangement which is etficient. employing short, directhydraulic connections and w h minimum fluid friction except when suchfriction is intentionally employed for control purposes.

It is another object to provide a novel control arrangement for a valveor the like which is extremely simple, having a minimum number of parts,and which secures modulated control of the valve position withoutcomplex position feed-hack arrangements conventionally resorted to amodulation systems. It is a related object to provide a control systemwhich is stable, free of detenting, capable of precise control, and withrapid response to changes in the condition.

It is a further object to provide a condition control device which,despite use of a constantly running motor and pump, is capable ofoperating without care or maintenance over long periods of time. It is arelated object Reissued Mar. 24, 1964 "ice to provide a valve operatorconsisting of but two control subasscmblics, easy of access, and eitherof which may be removed and replaced in a few moments time in the eventthat service becomes necessary.

In one of its aspects it is an object of the present invention toprovide a hydraulic amplifier energized by a transistor amplifier andwhich is, of itself, of extreme compactness, devoting minimum space to afiltered power supply and capable of stable operation with largepercentages of ripple in the nominally D.-C. portions of the circuit. Itis another object to provide a control system for an integratedtransistor amplifier which is sensitive to the phase as well as themagnitude of an A.-C. control signal. It is a more specific object inthis connection to provide a control system having a phase-sensitivetransistor circuit and employing an auxiliary A.-C. signal to establishthe operating position of the How control element which obtains at thecontrol point.

It is still another object to provide a condition control arrangementfor a radiator or heat exchanger particularly well suited for thecontrolling of hot water or the like in winter and a coolant in thesummer. It is a related object to provide a temperature control unitwhich may be switched from winter operation to summer operation simplyby reversing the phase of the alternating voltage which energizes theinput circuit and without changing the eiicctive control point. In thisconnection it is an object to provide a bridge circuit having asensitive resistauce element and so arranged that zero A.-C. signalvoltage is produced at the control point but with an auxiliary A.-C.signal being injected to establish operation of the transistor amplifierin both directions along the steep portion of the transistor outputcharacteristic.

Finally, it is an object to produce a compact unitary control devicewhich may be produced at such low cost as to enable a separate completecontrol system to be used for each radiator employed in a controlledspace thereby permitting zone control at a cost much less than that ofconventional zone control arrangements.

Other objects and advantages of the invention will become apparent uponreading the attached description and upon reference to the drawings inwhich:

FIGURE 1 is a vertical section of a unitary control device constructedin accordance with the present invention;

FIG. 2 is a horizonial fragmentary section taken along the line 2--2 inFIG. 1;

FIG. 3 is a fragmentary section taken along the line 33 in FIG. 2;

FIG. 4 is a fragmentary section taken along the line 4-4 in FIG. 3showing the gear pump profile;

FIG. 5 is a schematic diagram of the electrical portion of the device;

FIG. 6 shows the flow of current in the fluid relay in the absence ofbridge input signal.

FIGS. 7a and 7b show the effects of increasing the temperature above thecontrol point and decreasing the ternperature below the control point,respectively, in the winter" condition; and

FIGS. 8a and 8b show the effects of decreasing the temperature below thecontrol point and increasing the temperature above the control point,respectively, in the summer condition.

While the invention has been described in connection with the preferredembodiment, it will be understood that I do not intend to limit theinvention to the embodiment shown but intend to cover the variousalternative and equivalent arrangements which may be included within thespirit and scope of the appended claims.

Turning now to the drawings, FIGURE 1 shows a unitary conditioncontroller 10 having a housing 11 which includes three subasscmblics,namely, a transistor amplifier 12, a motor-hydraulic assembly 13 and afluid actuator 14. The fluid actuator serves to mount the unit on aplunger operated valve 15 having a valve disk 16 cooperating with avalve seat 17. The fluid actuator 14 is cylindrical and of limitedheight having a diaphragm 20 connected to a downwardly extending plunger21. The latter is slideably mounted in a cup-shaped insert 22 which isfitted into a cylindrical recess 23 formed in the underside of thehousing 11. For the purpose of biasing the diaphragm to its upwardposition, a return spring 25 is used in the form of a double coilsurrounding the plunger 21. The diaphragm 20 thus divides the spacewithin the actuator into what may be termed a fluid chamber 26 and aspring chamber 27. It will be understood that when hydraulic fluid isforced into the fluid chamber 26, this causes the diaphragm 20 tocompress the spring 25 thereby moving the plunger 21 downwardly to closethe valve. For a given applied pressure, move ment of the plunger willonly take place until the reactive force of the spring equals the totalfluid pressure acting upon the diaphragm, so that an equilibriumposition of the valve will tend to be established until some changeoccurs in the fluid pressure.

In accordance with the present invention a constantly running pump isprovided together with a novel fluid relay arrangement so that theoutput pressure of the pump which is applied to the actuator 14 variesin accordance with the current supplied by the transistor amplifier 12.In order to understand the pump and relay arrangement, reference is madeto FIGS. 2, 3 and 4 which show pertinent fragmentary cross sections.Further in accordance with the invention, the motor-hydraulic assembly13 includes an integral pump and fluid relay all integrally connected tothe frame of the driving motor to form a unitary assembly in the shapeof an inverted L. In the present embodiment the motor 30 has anupstanding core 31 having an offset field coil 32 at its lower end andan armature 33 extending transversely in its upper end. Comprising apart of the motor is a specially formed frame member 35 having a pair ofpump gears 36, 37 recessed therein (FIG. 4). The gear 36 is drivendirectly by a motor armature, and the gear 37 is simply an idler in meshtherewith. For the purpose of conducting fluid from the pump, a portmember 40 is provided secured to the frame member 35 by means of screwsor the like and having an inlet port 41, an outlet port 42 and a controlport 43, the latter being connected to the outlet port. For the purposeof controlling the pressure at the outlet, the control port 43 iscontrolled by a fluid relay 45. As illustrated, this relay extends offat right angles to the left of the motor and is rigidly secured to theport member 40.

In carrying out the invention, the fluid relay 45 includes an escapeorifice which is directly coupled to the control port of the pump andwhich is controllably blocked by the action of the relay armature,thereby to vary the orifice back pressure and hence the output pressureof the pump. In the present device the relay includes a magnetic frame46, a central magnetic core 47 of hollow construction terminating in anorifice 48, and a coil 49 surrounding the core. Extending flatly acrossthe orifice 48 is the relay armature 50 which, for convenience, may bemounted on a spring hinge 51. In order to avoid any detenting effect,the armature-core circuit preferably includes an air gap 52 when thearmature is in the fully closed, orifice-blocking position.

In accordance with one of the more detailed aspects of the invention,the armature is biased into the orificeblocking position, and novelmeans are provided for adjusting the biasing pressure, thereby to adjustthe inputoutput characteristics of the relay. In the present instancethe adjustable bias is provided by an auxiliary spring 53 which issecured, cantilever fashion, to the outer surface of the armature andwhich reacts against an adjustable stop 54. It will become apparent asthe discussion proceeds that simply by bending the adjustable stop 54inwardly or outwardly, the response characteristics of the relay, i.e.,the orifice established for a given relay current, may be convenientlychanged.

Reference may be made at this point to the novel interfitting relationwhich contributes largely to the compactness and hence utility of thepresent device. Thus, While the housing 11 is in the form of arectangular box, the cylindrical fluid actuator 14 is recessed into thebottom wall thereof, and a vertical partition indicated at 60 thusserves to divide the available remaining space into two compartments ofinverted L shape. The motorhydraulic assembly, which is also of L shapeas previously noted, may be thus compactly nested with respect to theactuator to produce what may be termed a wraparound" construction inwhich substantially all of the available space is utilized, whileproviding extremely short hydraulic connections. Moreover, the L shapedcompartment 11a is filled with fluid, preferably oil, up to the level 61which not only serves as a fluid sump for the hydraulic system but alsoinsures that the moving parts are constantly cooled and lubricated.Since the motor is constantly bathed in oil, it may be operatedindefinitely without necessity for relubrication. The motor-hydrauliccompartment is preferably sealed against the escape of fluid by adiaphragm 11d held in place by a cover 11c, the diaphragm being free tocome and go as the level of the hydraulic fluid changes. The space abovethe diaphragm is suitably vented. Conveniently, the motor-hydraulic unitmay be mounted on a pair of pedestals 62 and secured in place thereon bymachine screws 63 (the fastening means at one end only of the motorbeing visible). Thus, following removal of the cover and diaphragm, theentire unit may be removed for replacement simply by unscrewing thescrews 63.

The electrical portions of the device to be described (FIG. 5) may besimilarly disposed on an L shaped chassis 65 to fill the available spaceand enclosed by a light access cover 11d.

ELECTRICAL CIRCUIT Having understood the motor drive and mechanicalportions of the device, attention may next be given to the novelelectrical circuit which controls the operation of the mechanicalportion and which is coordinated therewith in a novel fashion to producethe desired over-all result. The circuit indicated generally at (FIG.5), may, for convenience, be viewed as a series of sub-circuits. Thefirst sub-circuit is a bridge circuit 101 having a main sensitiveresistor element 102 and an auxiliary element 103. The element 103 may,for example, be subjected to the outside ambient temperature to providemore precise control.

The second sub-circuit is the transistor input stage 104. The latterfeeds into a second transistor stage 105 which controls the coil 49 ofthe fluid relay previously referred to. Direct voltage is supplied tothe transistor circuit from a direct voltage supply 106 which isenergized from the regular A.-C. line via terminals 107. As will be morefully understood as the discussion proceeds, the current in the relaycoil 49 is established at a predetermined, steady-state value at thecontrol point, i.e., at the desired temperature and with zero outputsignal from the bridge. As the temperature varies in one direction orthe other, the relay current varies in one direction or the other fromthe steady-state value to produce corresponding positioning of thecontrol member with correct action at the control valve.

With regard to the details of the bridge 101, the sensitive elements102, 103 occupy diagonal positions in the bridge circuit. The remaininglegs comprise resistors 112, 113. Also included in the bridge is acalibrating potentiometer 114 which is connected to a grounded outputterminal 115, the signal output terminal being indicated at 116.

For the purpose of supplying the bridge with alternating voltage fromthe source 107, a transformer is provided having a primary winding 121and a secondary winding 122. As will be more fully disclosed, it is oneof the features of the present control arrangement that it permitswinter-summer operation. Thus the secondary winding 122 is divided intoportions of positive and negative phase having terminals 123, 124, and asingle pole, double throw switch 125 is provided to switch from onephase to the other. To adjust the magnitude of the signal voltageapplied to the amplifier, a voltage divider is connected to the outputterminal of the bridge consisting of a resistor 126 and potentiometer127 having a slider 128.

With regard to the first transistor stage, this includes a transistor130 having a base 131, an emitter 132, and a collector 133. In serieswith the emitter is an emitter resistor 134 which may have a value onthe order of 10,000 ohms for maximum temperature stability. Directvoltage for operating the transistor is obtained from a power supplyconsisting of a transformer winding on the transformer 120, a rectifier141, and a smoothing capacitor 142. Voltage is produced between anegative output terminal 143 and a positive output terminal 144.

For the purpose of coupling the transistor stages together, atransformer is used having a primary winding 151 and a secondary winding152. A capacitor 153 is shunted across the primary winding 151 toimprove the wave form. For maximum temperature stability of the secondtransistor stage, the secondary winding is preferably of extremely lowD.-C. resistance, on the order of 8 ohms. The first transistor is biasedto produce operation in a region of high signal amplification over awide range of ambient temperature so that the voltage appearing acrossthe secondary 152 of the coupling trans former consists of amplifiedalternating current, corresponding in phase but substantially greater inmagnitude than the output voltage of the bridge.

Coupled to the transformer 15% is an output transistor 169 having a base161, an emitter 162, and a collector 163. In order to make thetransistor stage 105 phase sensitive, the collector 163 is supplied withhalf waves of A.-C. rectified by a rectifier 164 which is connected tothe transformer winding 141 With regard to the bias of the second stage,such stage is preferably operated 1 Therefore, with no input signal, theoutput class B.

During the positive half current is effectively zero. cycle of the inputcurrent, the stage is driven into the class C range and is cut oilfurther. Output current flows only during the negative half cycles. Inseries with the collector is the coil 49 of the fluid relay. To smoothout the half cycles of current and thus prevent chattering of the rclayarmature, the relay coil is shunted by a capacitor 165.

In accordance with one of the aspects of the invention, an auxiliaryalternating voltage is applied to the input circuit of the transistor sothat even in the absence of signal voltage from the bridge (there beingno bridge output signal at the control point) a steady-state currentwill exist in the relay coil 49. In the present instance the auxiliaryvoltage is applied to the input of the transistor 16% via a seriesresistor 166 connected to the transformer secondary 14%. The voltage isinjected in the primary of the coupling transformer 15%. However, itwill be understood by those skilled in the art that the voltage may beinjected in the secondary of the coupling transformer if desired withoutsubstantially changing the operation of the circuit. The eitect of theauxiliary voltage will be more fully appreciated in connection withFIGS. 68 to be discussed.

It is one of the features of the present device that direct voltagecontaining a large component of A.-C. ripple may be tolerated from thepower supply 106 without adversely affecting the operation of thecircuit. In accordance with the present invention the common positivebus of the amplifier circuit is floating rather than being grounded tothe ground terminal of the detector circuit. To accomplish this floatingaction, a voltage divider consisting of resistors 171, 172 is providedat the output of the power supply having a common terminal 1'73 which isgrounded. Moreover, arranged in series with the emitter in the inputcircuit is a capacitor 174 which has such a high capacity as to olTerlow impedance at the signal and ripple frequency. This capacitor may,for example, have a capacity of 30 microfarads. Because of a low A.-C.impedance of the capacitor the ripple voltages applied to the base andemitter are substantially equal in phase and magnitude and hence noamplification of the ripple can occur in the first stage. Moreover, theimpedance of the primary winding 151 of the coupling transformer ispurposely made very low, on the order of 500 ohms, compared to therelatively high output impedance of the transistor. Hence the ripplepresent in the half wave rectified bias supply has a very small effecton the collector impedance. No ripple problem is raised by the secondtransistor stage since this stage is not fed by the direct voltagesupply. The net eltect is that large amounts of ripple may be toleratedwithout affecting the operation of the circuit even though the filtercapacitor 142, in the interests of extreme compactness. is of limitedsize and capacity.

Notwithstanding the lack of series resistance in the transistor inputcircuit, there is provision for applying direct bias between base andemitter. Such bias voltage is taken from across the capacitor 174, theamount of bias being such that operation takes place in a region oflarge signal amplification in spite of wide variations in transistorambient temperature.

A further advantage brought about by use of the coupling capacitor 174is that low impedances may be efficiently employed in the bridge andinput circuits. Thus it will be noted that there is no series resistancein the transistor input circuit. The only series impedance is thatprovided by the capacitor 174 but since, at signal frequency, thisimpedance is extremely low, the bridge circuit "sees only thebaseemitter impedance of the transistor. With a low impedance operatinginto a low impedance, transfer efficiency is maximum.

DESCRIPTION OF OPERATION While the manner in which the above componentsand subassemblies cooperate with one another in order to produce thedesired overall result will be apparent to one skilled in the art,nevertheless it will be helpful to describe the operation under thevarious typical circumstances. It will be assumed that the maintemperature responsive element 1% is in the space to be controlled andthe auxiliary element M13 is for the purpose of providing anticipationand reset. located in the outset ambient; however, in the description ofthe operation the auxiliary element 163 may be disregarded. It willfurther be assumed that the winter-summer switch 125 (FIG. 5) is in thewinter setting and that steam, hot water or the like is flowing throughthe valve 15 to the associated radiator. Finally, it will be assumedthat the temperature is at the control point. i.e., at 70. To set thecontrol point, the calibration potentiometer 114 may be adjusted so thatat the desired temperaure the output of the bridge circuit 101 appearingat terminal 116 is zero.

As described, it is one of the features of the present invention that atthe control point, with zero output voltage from the bridge circuit, apredetermined steady state current is caused to flow in the relay 45resulting from injection of the auxiliary A.-C. voltage. The relaycurrent may, in a practical case, be about 12.5 milliamperes. sufficientto develop a midrange pressure in the hydraulic system and actuator. andthus suificient to crack open the control valve to allow flow of the hotwater or the other controlled medium into the radiator. Under suchconditions, sufficient heating medium is ad- 7 mitted to make up for thelosses from the controlled space, and hence the temperature tends toremain in the vicinity of the control point.

It will be helpful to refer to FIG. 6 which shows this no signal"condition existing at the control point. The only signal being appliedto the output transistor 160 under such circumstance is the auxiliaryA.-C. voltage which is fed to the input of the transistor 160 throughthe resistor 166 (FIG. While the resistor is shown connected to theprimary of the transformer 150, a corresponding voltage will bedeveloped across the transformer secondary and hence applied to the baseor input circuit of the transistor. One cycle of input voltage isindicated at 180 in FIG. 6. Because of the action of the rectifier 164,only negative pulses 181 of current can flow through the transistor, andthen only when current is flowing in the negative direction in the baseof the transistor. It will thus be apparent that steady state currentwill flow in half-cycle pulses, and such half-cycle pulses have beenshown in FIGS. 6, 7 and 8. However, such figures are diagrammatic andfor the purpose of illustrating phase relationships. The actual currentthrough the relay coil tends to persist between the halfcycles due tothe storage action of the shunt capacitor 165.

To show the eflect of an increase in the temperature of the controlpoint, reference is made to FIG. 7a. An increase in temperature causesthe bridge output appearing at terminal 116 to depart from zero inpredetermined phase. The phase of the resulting bridge signal, shown at182 and as applied to the input of the second transistor stage, is insuch a direction as to coincide in phase with the auxiliary A.-C.signal, so that the effect is to increase the magnitude of the signalapplied at the input of the second transistor to the value indicated at183 in FIG. 7a. This produces a corresponding increase in the current184 flowing through the coil of the relay 45. The increase in thecurrent in the relay causes the armature 50 to be drawn down moretightly against the orifice 48, thereby increasing the back pressure inthe hydraulic system and increasing the pressure exisiting in theactuator. The effect of this is that the diaphragm moves downwardly anincremental amount until the force behind it is opposed by an equalspring force, at which point further movement of the diaphragm will nottake place. L

as a result, the valve disk 16 is moved toward the valve seat therebyfurther throttling flow of the water or other heated medium to thevalve. The reduced flow results in a lowered radiator temperature andhence tends to counteract the change in the condition within the spacewhich set the corrective cycle in motion.

The opposite corrective action takes place upon an assumed decrease inambient temperature in the heated space. A decrease in temperatureproduces a bridge output voltage of opposite phase as indicated at 185in FIG. 7b. The signal from the bridge thus tends to be subtracted fromthe auxiliary steady state A.-C. signal 180 to form a net input signalto the second transistor as indicated at 186. This decrease in the inputsignal results in a corresponding decrease in the output current asindicated at 187, so that the current through the relay becomes lessthan the steady state value. This causes the armature to be lessstrongly attracted, which tends to open the escape orifice 48 so that alower pressure of fluid exists in the actuator, causing the valveplunger to move slightly in the upward direction until a force balancewith the return spring is achieved. The effect is to open the valve anadditional amount, thereby permitting fluid to flow to the radiator tobring the temperature of the controlled space back to the control point.

Analogous operation occurs during the summer season, assuming thatcoolant is to be circulated through the radiator, for example, in theform of cold water. To establish summer operation it is sufiicient tothrow the switch 125 to the summer" position. It is to be noted that atthe control point throwing the switch from one position to the other hasno effect upon the bridge output since the output in either event iszero. However, the result of throwing the switch is to change the phaseso that the signal from the bridge, upon departure of temperature in agiven direction, is in the opposite sense with respect to the auxiliarysignal injected by the resistor 16-6.

Referring to FIG. 8a and assuming that the temperature in the spacemoves above the control point, the bridge signal 188 subtracts from thesteady state signal 180 to produce a net signal 189 which produces alowered value of current through the relay as indicated at 190. Thisbrings about a decrease in the pressure within the actuator causing thevalve 15 to be opened to admit additional coolant, thereby to restorethe temperature to the control point. In the event the temperature dropsbelow the control point, as in FIG. 8b, a signal 191 is produced whichis in phase with the auxiliary injected signal to produce a net signal192 at the input of the second transistor which results in an increasedcurrent 193 flowing through the relay. The effect of the increasedcurrent is to tend to throttle down the flow of coolant to the radiator,thereby permitting the temperature in the controlled space to increaseback to the control point. Precise modulation is thereby achieved, withmore accurate control than is afforded by rudimentary types of on-offradiator control devices. In other words, the present unitary controldevice, in the space of only a few cubic inches, accomplishes the sameresult as elaborate built-in and expensive systems. It is to be notedthat modulated control is achieved with a minimum of parts and withoutnecessity for a position follow-up or feedback linkage of the type usedin conventional servo control systems.

While the device is distinguished by a low level of power in theamplifier circuits and use of a low-torque motor, nevertheless,experience has shown that forces may be developed at the valve plungerwhich are adequate to overcome friction or stickiness of the packing orsticking at the valve seat even after the device has been dormant for aperiod of several months. The reason for this is that the motor need notbe capable of rapidly driving the diaphragm against the force of thespring but need only have the power to produce incremental movement ofthe diaphragm in the face of the minor changes in temperature whichoccur in the control of space temperature. Moreover, the relativelysmall displacement of the gear pump produces a powerful force-amplifyingeffect. Provided that a diaphragm of reasonable area is employed,operating forces may be developed which are even more powerful than theforces developed using a stepdown gear train and without danger ofbreaking or stripping the high-torque gears in the train. Moreover, itis to be noted that the mechanical complexity and loss due to friction,except for the intentional loss at the orifice for control purposes, ismuch lower than in conventional radiator control arrangements.

It has been found that a sufficiently high amplification factor can beachieved in the fluid relay so that the current load imposed upon theoutput transistor may be kept well within the rating of conventionaltransistors, i.e., no special "power transistor need be used. All of theparts are employed well within their ratings so that the device may beexpected to operate more or less indefiinitely, electrically, as well asmechanically.

Nor is there any tendency for the control arrangement to become unstablein the face of high ambient temperatures as may exist around asteam-heated radiator. In the first place, the input transistor isprovided with an emitter resistor 134 having a value which issubstantially greater than that conventionally used and which may, forexample, be about 10,000 ohms. Thus, any changes in the emitterresistance brought about by changes in ambient temperature produce onlya minor percentage change in the characteristics of the transistor andthere is no danger of thermal runway. While this involves some sacrificein voltage gain, the voltage gain in the first stage neverthelessadequate. In the second transistor stage, temperature stability isachieved by using a transformer 150 having a secondary with low D.-C.resistance, so that the base and emitter are kept effectively at thesame D.-C. level. As a result the device as a whole may be operated attemperatures toward the upper level of the transistor temperatureratings but with perfect reliability as far as the transistorcharacteristics are concerned.

It will be apparent to one skilled in the art that the device describedabove satisfies the divergent space and performance requirements foreffective radiator temperature control and may be manufactured at asufficiently low cost to enable each radiator to be equipped with itsown complete unit. Little or no maintenance is required. It will beapparent to one skilled in the art that the same unit may be employedfor controlling a damper instead of a valve or may be used to controlother conditions by a suitable change in the sensitive element withoutdeparting from the invention.

In the following claims the term bellows is intended to be genericapplying to any diaphragm or bellows actuator having a sealed fluidcompartment. The term fluid relay is intended to cover devices in whicha change in current results in a change in the pressure applied to ahydraulic actuator. The term back pressure refers to the pressure whichexists on the upstream side of the escape orifice.

We claim as our invention:

1. An automatic valve operator comprising in combination a cylindricalactuator having a plunger, a diaphragm in said actuator, a spring forpressing against said diaphragm, an outer enclosure secured to saidactuator and therewith defining first and second compartments ofL-shaped cross section, a motor assembly including a motor having anintegral gear pump and a fluid relay secured thereto extending at rightangles to the motor in L-shaped relation, said motor assembly beingnestingly fitted in said first L-shaped compartment, said fluid relayhaving a coil and armature and having an escape orifice with a directconnection to said fluid pump, said armature being arranged to blocksaid orifice in accordance with the variable current flowing throughsaid coil to produce a variable back pressure, a conduit for connectingthe output of said gear pump to said fluid actuator so that thevariations in said back pressure produce corresponding variations in theposition of said plunger, and an amplifier for supplying said coiltotally contained in said second L-shaped compartment.

[2. An automatic valve operator comprising in combination a constantlyrunning drive motor having a motor frame, a gear pump including a pairof gears in said frame running in meshed engagement, means in said framedefining an inlet port and an outlet port, a fluid relay having a coiland a hollow magnetic core terminating in an orifice, said fluid relaybeing integral with said frame so that the outlet port communicatesdirectly with the hollow magnetic core, said fluid relay having anarmature for blocking said orifice, means providing an air gap in themagnetic circuit formed by the core and armature when the armature is inits fully blocking relation, a fluid actuator having a plunger and afluid chamber, said fluid chamber being connected to the outlet port, areturn spring for opposing movement of said plunger so that the plungeroccupies in a position dependent upon the current flowing in said coil,and means for supplying variable current to said coil] 3. An automaticvalve operator comprising a housing, a cylindrical recess in theunderside of the housing, a cup-shaped insert fitting into said recess,a plunger slideably mounted in said insert, a diaphragm covering themouth of the insert for defining a fluid chamber for exerting pressureagainst said plunger, a return spring surrounding the plunger forreacting against said diaphragm, a constantly running motor in saidhousing having a frame and having a downwardly offset field portionadjacent said recess with the motor shaft above the level of saidrecess, a gear pump in said motor frame having an inlet and an outlet, afluid relay integrally mounted on said motor frame at the output of thegear pump and in a position overhanging said recess, said fluid relayhaving a coil and armature and a fluid orifice blocked by the armature,means for energizing the coil with variable current thereby to vary theback pressure at the output of the gear pump, and a conduit for couplingthe outlet of the gear pump to said fluid chamber, said housing beingfilled with fluid to a point above the inlet of said gear pump.

4, In an automatic valve operator for a radiator or the like having areciprocable valve element, the combination comprising a hollow framehaving provision for mounting on a radiator and having a movablediaphragm defining a pressure chamber on one side thereof and a springchamber on the other side, a plunger coupled to the diaphragm and havingprovision for connection to the reciprocable valve element, a spring inthe spring chamber for opposing movement of the diaphragm in response toentry of hydraulic fluid into the pressure chamber, said frame defininga motor chamber integral therewith immediately adjacent the pressurechamber and containing a body of hydraulic fluid, a constantly runningmotor in said motor chamber submerged in the fluid, said motor having apumpclosely coupled thereto, said pump having an input connection fordrawing fluid from said body of fluid and having an outlet connectionconnected to the adjacent pressure chamber, a fluid relay integral withsaid pump having an orifice connected to the outlet of the pump andhaving a movable armature for controllably blocking the escape of fluidfrom said outlet into said body of fluid thereby to vary the pressure ofthe fluid admitted to the pressure chamber, a temperature sensingdevice, an amplifier in said hollow frame but isolated from the motorchamber for applying a reference value of current to the relay when thetemperature is at a desired control point and for varying the currentabove and below the reference value in accordance with variations intemperature thereby to produce corrective movement of the valve plungerfor maintenance of a predetermined temperature condition.

5. In a temperature control system for a controlled space and having amember for controlling the flow of heat relative to the space, thecombination comprising an A.-C. source, a bridge circuit including atemperature sensitive element and energized by said A.-C. source forproduction of a signal which varies in phase and amplitude in accordancewith the direction and magnitude of the departure of the temperaturefrom a desired control point, an amplifier having an input and an outputwith the input being coupled to said bridge, means for supplying theamplifier output circuit with half waves of A.-C. from said source, afluid relay having an orifice and an armature for controlling escape offluid from the orifice, said fluid relay being connected in theamplifier output circuit so that the current flowing in said relayvaries in accordance with the temperature, a fluid actuator having areturn spring, a constantly running motor permanently connected to theAC. source, said motor having close-coupled thereto a fluid pump havingits output connection connected to the orifice of said fluid relay andto said actuator so that the pressure in said actuator varies inaccordance with the current in said relay, said amplifier being soconstructed and arranged that a steady state reference current exists insaid fluid relay at the control point and in the absence of a signalfrom said bridge circuit, and means for selectively reversing the phaseof the alternating voltage supplied to the bridge circuit thereby toreverse the direction of movement of the flow controlling member whendeparture of the temperature occurs in a given direction from thecontrol point for winter-summer operation at the same control pointindependently of making any change in the circuit other than saidselective reversal of phase.

6. An automatic valve operator comprising, in combination, a housing aconstantly running drive motor mounted in said housing and having amotor frame, a pump driven by said motor and having an inlet side and anoutlet side, means in said frame defining an inlet port and an outletport communicating respectively with the inlet side and the outlet sideof said pump, a sump formed in said housing and communicating with saidinlet port whereby said pump draws fluid from said sump and pumps saidfluid through said outlet port, a fluid actuator in said housingincluding a reciprocable plunger and a fluid chamber on one side of saidplunger, said fluid chamber communicating with said outlet port toreceive fluid from said pump whereby said plunger is urged in onedirection, a return spring opposing movement of said plunger in said onedirection, a fluid relay in said housing having a coil and a hollowmagnetic core terminating in an orifice, said fluid relay being rigidlymounted with respect to said frame with said hollow magnetic corecommunicating directly with said fluid chamber whereby said chamber,said core and said pump are in direct communication, means for supplyingvariable current to said coil, said fluid relay having an armaturedisposed across and variably attracted toward said orifice to restrictthe flow of fluid through said core in accordance with the magnitude ofcurrent flowing through said coil thereby to control the pressure insaid chamber, and means providing an air gap in the magnetic circuitformed by the core and armature when the armature is in its fullyblocking position.

7. In a hydraulic actuator, first and second variable volume chambers,the combined volume of said two chambers remaining constant and being atleast substantially filled with hydraulic fluid, constantly running pumpmeans in one of said chambers having a suction port in communicationwith said first chamber and an outlet port in communication with saidsecond chamber for pumping fluid from said first chamber into the secondchamber, each of said chambers having a movable wall whereby the pumpoutput urges the movable wall of said second chamber in one direction toexpand the second chamber, equalizing means for opposing movement ofsaid second chamber wall in said one direction, a fluid return vent fromsaid second chamber to said first chamber, and a selectively variablefluid flow restrictor for varying the flow through said vent thereby tocreate a back pressure in said second chamber balancing against theopposing force of said equalizing means and causing said second chamberwall to assume a position dependent upon the amount of restriction ofsaid vent, said flow restrictor including a member disposed across butnormally spaced from said return vent and movable from a maximumdistance away from said vent to a position in which the vent is closed,and means for urging said member toward said vent with a selectivelyvariable force which determines the back pressure in said second chamberand positions said second chamber wall in accordance with the magnitudeof said variable force.

8. A hydraulic actuator as defined in claim 7 further including a deviceresponsive to variations in a measured condition and operable to varysaid force in accordance with variations in said condition.

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